Reactivity of sera and synovial fluids from patients with rheumatoid arthritis and nonrheumatic diseases will be tested for antibody activity to cell surface antigens on cultured synovial cells. We are testing the hypothesis that the antibodies reactive with these antigens are complexed to antiglobulins. Thus samples will be tested for antibody activity by indirect immunofluorescence before and after adsorption of antiglobulin. Cross reactivity of the anti-synovial antibodies with vival, bacterial and mycoplasma antigens will be examined at a later date.